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gecko/js/src/jsscope.h

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/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sw=4 et tw=99:
*
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Communicator client code, released
* March 31, 1998.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1998
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef jsscope_h___
#define jsscope_h___
/*
* JS symbol tables.
*/
#ifdef DEBUG
#include <stdio.h>
#endif
#include "jstypes.h"
#include "jscntxt.h"
#include "jslock.h"
#include "jsobj.h"
#include "jsprvtd.h"
#include "jspubtd.h"
#include "jspropertycache.h"
#include "jspropertytree.h"
#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable:4800)
#pragma warning(push)
#pragma warning(disable:4100) /* Silence unreferenced formal parameter warnings */
#endif
JS_BEGIN_EXTERN_C
/*
* Given P independent, non-unique properties each of size S words mapped by
* all scopes in a runtime, construct a property tree of N nodes each of size
* S+L words (L for tree linkage). A nominal L value is 2 for leftmost-child
* and right-sibling links. We hope that the N < P by enough that the space
* overhead of L, and the overhead of scope entries pointing at property tree
* nodes, is worth it.
*
* The tree construction goes as follows. If any empty scope in the runtime
* has a property X added to it, find or create a node under the tree root
* labeled X, and set scope->lastProp to point at that node. If any non-empty
* scope whose most recently added property is labeled Y has another property
* labeled Z added, find or create a node for Z under the node that was added
* for Y, and set scope->lastProp to point at that node.
*
* A property is labeled by its members' values: id, getter, setter, slot,
* attributes, tiny or short id, and a field telling for..in order. Note that
* labels are not unique in the tree, but they are unique among a node's kids
* (barring rare and benign multi-threaded race condition outcomes, see below)
* and along any ancestor line from the tree root to a given leaf node (except
* for the hard case of duplicate formal parameters to a function).
*
* Thus the root of the tree represents all empty scopes, and the first ply
* of the tree represents all scopes containing one property, etc. Each node
* in the tree can stand for any number of scopes having the same ordered set
* of properties, where that node was the last added to the scope. (We need
* not store the root of the tree as a node, and do not -- all we need are
* links to its kids.)
*
* Sidebar on for..in loop order: ECMA requires no particular order, but this
* implementation has promised and delivered property definition order, and
* compatibility is king. We could use an order number per property, which
* would require a sort in js_Enumerate, and an entry order generation number
* per scope. An order number beats a list, which should be doubly-linked for
* O(1) delete. An even better scheme is to use a parent link in the property
* tree, so that the ancestor line can be iterated from scope->lastProp when
* filling in a JSIdArray from back to front. This parent link also helps the
* GC to sweep properties iteratively.
*
* What if a property Y is deleted from a scope? If Y is the last property in
* the scope, we simply adjust the scope's lastProp member after we remove the
* scope's hash-table entry pointing at that property node. The parent link
* mentioned in the for..in sidebar above makes this adjustment O(1). But if
* Y comes between X and Z in the scope, then we might have to "fork" the tree
* at X, leaving X->Y->Z in case other scopes have those properties added in
* that order; and to finish the fork, we'd add a node labeled Z with the path
* X->Z, if it doesn't exist. This could lead to lots of extra nodes, and to
* O(n^2) growth when deleting lots of properties.
*
* Rather, for O(1) growth all around, we should share the path X->Y->Z among
* scopes having those three properties added in that order, and among scopes
* having only X->Z where Y was deleted. All such scopes have a lastProp that
* points to the Z child of Y. But a scope in which Y was deleted does not
* have a table entry for Y, and when iterating that scope by traversing the
* ancestor line from Z, we will have to test for a table entry for each node,
* skipping nodes that lack entries.
*
* What if we add Y again? X->Y->Z->Y is wrong and we'll enumerate Y twice.
* Therefore we must fork in such a case if not earlier, or do something else.
* We used to fork on the theory that set after delete is rare, but the Web is
* a harsh mistress, and we now convert the scope to a "dictionary" on first
* delete, to avoid O(n^2) growth in the property tree.
*
* What about thread safety? If the property tree operations done by requests
* are find-node and insert-node, then the only hazard is duplicate insertion.
* This is harmless except for minor bloat. When all requests have ended or
* been suspended, the GC is free to sweep the tree after marking all nodes
* reachable from scopes, performing remove-node operations as needed.
*
* Is the property tree worth it compared to property storage in each table's
* entries? To decide, we must find the relation <> between the words used
* with a property tree and the words required without a tree.
*
* Model all scopes as one super-scope of capacity T entries (T a power of 2).
* Let alpha be the load factor of this double hash-table. With the property
* tree, each entry in the table is a word-sized pointer to a node that can be
* shared by many scopes. But all such pointers are overhead compared to the
* situation without the property tree, where the table stores property nodes
* directly, as entries each of size S words. With the property tree, we need
* L=2 extra words per node for siblings and kids pointers. Without the tree,
* (1-alpha)*S*T words are wasted on free or removed sentinel-entries required
* by double hashing.
*
* Therefore,
*
* (property tree) <> (no property tree)
* N*(S+L) + T <> S*T
* N*(S+L) + T <> P*S + (1-alpha)*S*T
* N*(S+L) + alpha*T + (1-alpha)*T <> P*S + (1-alpha)*S*T
*
* Note that P is alpha*T by definition, so
*
* N*(S+L) + P + (1-alpha)*T <> P*S + (1-alpha)*S*T
* N*(S+L) <> P*S - P + (1-alpha)*S*T - (1-alpha)*T
* N*(S+L) <> (P + (1-alpha)*T) * (S-1)
* N*(S+L) <> (P + (1-alpha)*P/alpha) * (S-1)
* N*(S+L) <> P * (1/alpha) * (S-1)
*
* Let N = P*beta for a compression ratio beta, beta <= 1:
*
* P*beta*(S+L) <> P * (1/alpha) * (S-1)
* beta*(S+L) <> (S-1)/alpha
* beta <> (S-1)/((S+L)*alpha)
*
* For S = 6 (32-bit architectures) and L = 2, the property tree wins iff
*
* beta < 5/(8*alpha)
*
* We ensure that alpha <= .75, so the property tree wins if beta < .83_. An
* average beta from recent Mozilla browser startups was around .6.
*
* Can we reduce L? Observe that the property tree degenerates into a list of
* lists if at most one property Y follows X in all scopes. In or near such a
* case, we waste a word on the right-sibling link outside of the root ply of
* the tree. Note also that the root ply tends to be large, so O(n^2) growth
* searching it is likely, indicating the need for hashing (but with increased
* thread safety costs).
*
* If only K out of N nodes in the property tree have more than one child, we
* could eliminate the sibling link and overlay a children list or hash-table
* pointer on the leftmost-child link (which would then be either null or an
* only-child link; the overlay could be tagged in the low bit of the pointer,
* or flagged elsewhere in the property tree node, although such a flag must
* not be considered when comparing node labels during tree search).
*
* For such a system, L = 1 + (K * averageChildrenTableSize) / N instead of 2.
* If K << N, L approaches 1 and the property tree wins if beta < .95.
*
* We observe that fan-out below the root ply of the property tree appears to
* have extremely low degree (see the MeterPropertyTree code that histograms
* child-counts in jsscope.c), so instead of a hash-table we use a linked list
* of child node pointer arrays ("kid chunks"). The details are isolated in
* jsscope.c; others must treat JSScopeProperty.kids as opaque. We leave it
* strongly typed for debug-ability of the common (null or one-kid) cases.
*
* One final twist (can you stand it?): the mean number of entries per scope
* in Mozilla is < 5, with a large standard deviation (~8). Instead of always
* allocating scope->table, we leave it null while initializing all the other
* scope members as if it were non-null and minimal-length. Until a property
* is added that crosses the threshold of 6 or more entries for hashing, we use
* linear search from scope->lastProp to find a given id, and save on the space
* overhead of a hash table.
*
* See jspropertytree.{h,cpp} for the actual PropertyTree implementation. This
* file contains object property map (historical misnomer: "scope" AKA JSScope)
* and property tree node ("sprop", JSScopeProperty) declarations.
*/
struct JSEmptyScope;
#define SPROP_INVALID_SLOT 0xffffffff
struct JSScope : public JSObjectMap
{
#ifdef JS_THREADSAFE
JSTitle title; /* lock state */
#endif
JSObject *object; /* object that owns this scope */
uint32 freeslot; /* index of next free slot in object */
uint8 flags; /* flags, see below */
int8 hashShift; /* multiplicative hash shift */
uint16 spare; /* reserved */
uint32 entryCount; /* number of entries in table */
uint32 removedCount; /* removed entry sentinels in table */
JSScopeProperty **table; /* table of ptrs to shared tree nodes */
JSEmptyScope *emptyScope; /* cache for getEmptyScope below */
/*
* A little information hiding for scope->lastProp, in case it ever becomes
* a tagged pointer again.
*/
inline JSScopeProperty *lastProperty() const;
private:
JSScopeProperty *getChildProperty(JSContext *cx, JSScopeProperty *parent,
JSScopeProperty &child);
JSScopeProperty *newDictionaryProperty(JSContext *cx, const JSScopeProperty &child,
JSScopeProperty **childp);
bool toDictionaryMode(JSContext *cx, JSScopeProperty *&aprop);
/*
* Private pointer to the last added property and methods to manipulate the
* list it links among properties in this scope. The {remove,insert} pair
* for DictionaryProperties assert that the scope is in dictionary mode and
* any reachable properties are flagged as dictionary properties.
*
* NB: these private methods do *not* update this scope's shape to track
* lastProp->shape after they finish updating the linked list in the case
* where lastProp is updated. It is up to calling code in jsscope.cpp to
* call updateShape(cx) after updating lastProp.
*/
JSScopeProperty *lastProp;
/* These four inline methods are defined further below in this .h file. */
inline void setLastProperty(JSScopeProperty *sprop);
inline void removeLastProperty();
inline void removeDictionaryProperty(JSScopeProperty *sprop);
inline void insertDictionaryProperty(JSScopeProperty *sprop, JSScopeProperty **childp);
/* Defined in jsscopeinlines.h to avoid including implementation dependencies here. */
inline void updateShape(JSContext *cx);
inline void updateFlags(const JSScopeProperty *sprop);
protected:
void initMinimal(JSContext *cx, uint32 newShape);
private:
bool createTable(JSContext *cx, bool report);
bool changeTable(JSContext *cx, int change);
void reportReadOnlyScope(JSContext *cx);
void setOwnShape() { flags |= OWN_SHAPE; }
void clearOwnShape() { flags &= ~OWN_SHAPE; }
void generateOwnShape(JSContext *cx);
JSScopeProperty **searchTable(jsid id, bool adding);
inline JSScopeProperty **search(jsid id, bool adding);
inline JSEmptyScope *createEmptyScope(JSContext *cx, JSClass *clasp);
JSScopeProperty *addPropertyHelper(JSContext *cx, jsid id,
JSPropertyOp getter, JSPropertyOp setter,
uint32 slot, uintN attrs,
uintN flags, intN shortid,
JSScopeProperty **spp);
public:
JSScope(const JSObjectOps *ops, JSObject *obj)
: JSObjectMap(ops, 0), object(obj) {}
/* Create a mutable, owned, empty scope. */
static JSScope *create(JSContext *cx, const JSObjectOps *ops,
JSClass *clasp, JSObject *obj, uint32 shape);
void destroy(JSContext *cx);
/*
* Return an immutable, shareable, empty scope with the same ops as this
* and the same freeslot as this had when empty.
*
* If |this| is the scope of an object |proto|, the resulting scope can be
* used as the scope of a new object whose prototype is |proto|.
*/
inline JSEmptyScope *getEmptyScope(JSContext *cx, JSClass *clasp);
inline bool ensureEmptyScope(JSContext *cx, JSClass *clasp);
inline bool canProvideEmptyScope(JSObjectOps *ops, JSClass *clasp);
JSScopeProperty *lookup(jsid id);
inline bool hasProperty(jsid id) { return lookup(id) != NULL; }
inline bool hasProperty(JSScopeProperty *sprop);
/* Add a property whose id is not yet in this scope. */
JSScopeProperty *addProperty(JSContext *cx, jsid id,
JSPropertyOp getter, JSPropertyOp setter,
uint32 slot, uintN attrs,
uintN flags, intN shortid);
/* Add a data property whose id is not yet in this scope. */
JSScopeProperty *addDataProperty(JSContext *cx, jsid id, uint32 slot, uintN attrs) {
JS_ASSERT(!(attrs & (JSPROP_GETTER | JSPROP_SETTER)));
return addProperty(cx, id, NULL, NULL, slot, attrs, 0, 0);
}
/* Add or overwrite a property for id in this scope. */
JSScopeProperty *putProperty(JSContext *cx, jsid id,
JSPropertyOp getter, JSPropertyOp setter,
uint32 slot, uintN attrs,
uintN flags, intN shortid);
/* Change the given property into a sibling with the same id in this scope. */
JSScopeProperty *changeProperty(JSContext *cx, JSScopeProperty *sprop,
uintN attrs, uintN mask,
JSPropertyOp getter, JSPropertyOp setter);
/* Remove id from this scope. */
bool removeProperty(JSContext *cx, jsid id);
/* Clear the scope, making it empty. */
void clear(JSContext *cx);
/* Extend this scope to have sprop as its last-added property. */
void extend(JSContext *cx, JSScopeProperty *sprop);
/*
* Read barrier to clone a joined function object stored as a method.
* Defined in jsscopeinlines.h, but not declared inline per standard style
* in order to avoid gcc warnings.
*/
bool methodReadBarrier(JSContext *cx, JSScopeProperty *sprop, jsval *vp);
/*
* Write barrier to check for a method value change. Defined inline below
* after methodReadBarrier. Two flavors to handle JSOP_*GVAR, which deals
* in slots not sprops, while not deoptimizing to map slot to sprop unless
* flags show this is necessary. The methodShapeChange overload (directly
* below) parallels this.
*/
bool methodWriteBarrier(JSContext *cx, JSScopeProperty *sprop, jsval v);
bool methodWriteBarrier(JSContext *cx, uint32 slot, jsval v);
void trace(JSTracer *trc);
void deletingShapeChange(JSContext *cx, JSScopeProperty *sprop);
bool methodShapeChange(JSContext *cx, JSScopeProperty *sprop);
bool methodShapeChange(JSContext *cx, uint32 slot);
void protoShapeChange(JSContext *cx);
void shadowingShapeChange(JSContext *cx, JSScopeProperty *sprop);
bool globalObjectOwnShapeChange(JSContext *cx);
/* By definition, hashShift = JS_DHASH_BITS - log2(capacity). */
#define SCOPE_CAPACITY(scope) JS_BIT(JS_DHASH_BITS-(scope)->hashShift)
enum {
DICTIONARY_MODE = 0x0001,
SEALED = 0x0002,
BRANDED = 0x0004,
INDEXED_PROPERTIES = 0x0008,
OWN_SHAPE = 0x0010,
METHOD_BARRIER = 0x0020,
/*
* This flag toggles with each shape-regenerating GC cycle.
* See JSRuntime::gcRegenShapesScopeFlag.
*/
SHAPE_REGEN = 0x0040,
/* The anti-branded flag, to avoid overspecializing. */
GENERIC = 0x0080
};
bool inDictionaryMode() { return flags & DICTIONARY_MODE; }
void setDictionaryMode() { flags |= DICTIONARY_MODE; }
void clearDictionaryMode() { flags &= ~DICTIONARY_MODE; }
/*
* Don't define clearSealed, as it can't be done safely because JS_LOCK_OBJ
* will avoid taking the lock if the object owns its scope and the scope is
* sealed.
*/
bool sealed() { return flags & SEALED; }
void seal(JSContext *cx) {
JS_ASSERT(!isSharedEmpty());
JS_ASSERT(!sealed());
generateOwnShape(cx);
flags |= SEALED;
}
/*
* A branded scope's object contains plain old methods (function-valued
* properties without magic getters and setters), and its scope->shape
* evolves whenever a function value changes.
*/
bool branded() { JS_ASSERT(!generic()); return flags & BRANDED; }
bool brand(JSContext *cx, uint32 slot, jsval v) {
JS_ASSERT(!branded());
generateOwnShape(cx);
if (js_IsPropertyCacheDisabled(cx)) // check for rt->shapeGen overflow
return false;
flags |= BRANDED;
return true;
}
bool generic() { return flags & GENERIC; }
void setGeneric() { flags |= GENERIC; }
bool hadIndexedProperties() { return flags & INDEXED_PROPERTIES; }
void setIndexedProperties() { flags |= INDEXED_PROPERTIES; }
bool hasOwnShape() { return flags & OWN_SHAPE; }
bool hasRegenFlag(uint8 regenFlag) { return (flags & SHAPE_REGEN) == regenFlag; }
/*
* A scope has a method barrier when some compiler-created "null closure"
* function objects (functions that do not use lexical bindings above their
* scope, only free variable names) that have a correct JSSLOT_PARENT value
* thanks to the COMPILE_N_GO optimization are stored as newly added direct
* property values of the scope's object.
*
* The de-facto standard JS language requires each evaluation of such a
* closure to result in a unique (according to === and observable effects)
* function object. ES3 tried to allow implementations to "join" such
* objects to a single compiler-created object, but this makes an overt
* mutation hazard, also an "identity hazard" against interoperation among
* implementations that join and do not join.
*
* To stay compatible with the de-facto standard, we store the compiler-
* created function object as the method value and set the METHOD_BARRIER
* flag.
*
* The method value is part of the method property tree node's identity, so
* it effectively brands the scope with a predictable shape corresponding
* to the method value, but without the overhead of setting the BRANDED
* flag, which requires assigning a new shape peculiar to each branded
* scope. Instead the shape is shared via the property tree among all the
* scopes referencing the method property tree node.
*
* Then when reading from a scope for which scope->hasMethodBarrier() is
* true, we count on the scope's qualified/guarded shape being unique and
* add a read barrier that clones the compiler-created function object on
* demand, reshaping the scope.
*
* This read barrier is bypassed when evaluating the callee sub-expression
* of a call expression (see the JOF_CALLOP opcodes in jsopcode.tbl), since
* such ops do not present an identity or mutation hazard. The compiler
* performs this optimization only for null closures that do not use their
* own name or equivalent built-in references (arguments.callee).
*
* The BRANDED write barrier, JSScope::methodWriteBarrer, must check for
* METHOD_BARRIER too, and regenerate this scope's shape if the method's
* value is in fact changing.
*/
bool hasMethodBarrier() { return flags & METHOD_BARRIER; }
void setMethodBarrier() { flags |= METHOD_BARRIER; }
/*
* Test whether this scope may be branded due to method calls, which means
* any assignment to a function-valued property must regenerate shape; else
* test whether this scope has method properties, which require a method
* write barrier.
*/
bool
brandedOrHasMethodBarrier() { return flags & (BRANDED | METHOD_BARRIER); }
bool isSharedEmpty() const { return !object; }
static bool initRuntimeState(JSContext *cx);
static void finishRuntimeState(JSContext *cx);
};
struct JSEmptyScope : public JSScope
{
JSClass * const clasp;
jsrefcount nrefs; /* count of all referencing objects */
JSEmptyScope(JSContext *cx, const JSObjectOps *ops, JSClass *clasp);
void hold() {
/* The method is only called for already held objects. */
JS_ASSERT(nrefs >= 1);
JS_ATOMIC_INCREMENT(&nrefs);
}
void drop(JSContext *cx) {
JS_ASSERT(nrefs >= 1);
JS_ATOMIC_DECREMENT(&nrefs);
if (nrefs == 0)
destroy(cx);
}
/*
* Optimized version of the drop method to use from the object finalizer
* to skip expensive JS_ATOMIC_DECREMENT.
*/
void dropFromGC(JSContext *cx) {
#ifdef JS_THREADSAFE
JS_ASSERT(CX_THREAD_IS_RUNNING_GC(cx));
#endif
JS_ASSERT(nrefs >= 1);
--nrefs;
if (nrefs == 0)
destroy(cx);
}
};
inline bool
JS_IS_SCOPE_LOCKED(JSContext *cx, JSScope *scope)
{
return JS_IS_TITLE_LOCKED(cx, &scope->title);
}
inline JSScope *
JSObject::scope() const
{
JS_ASSERT(isNative());
return (JSScope *) map;
}
inline uint32
JSObject::shape() const
{
JS_ASSERT(map->shape != JSObjectMap::SHAPELESS);
return map->shape;
}
inline jsval
JSObject::lockedGetSlot(uintN slot) const
{
OBJ_CHECK_SLOT(this, slot);
return this->getSlot(slot);
}
inline void
JSObject::lockedSetSlot(uintN slot, jsval value)
{
OBJ_CHECK_SLOT(this, slot);
this->setSlot(slot, value);
}
/*
* Helpers for reinterpreting JSPropertyOp as JSObject* for scripted getters
* and setters.
*/
namespace js {
inline JSObject *
CastAsObject(JSPropertyOp op)
{
return JS_FUNC_TO_DATA_PTR(JSObject *, op);
}
inline jsval
CastAsObjectJSVal(JSPropertyOp op)
{
return OBJECT_TO_JSVAL(JS_FUNC_TO_DATA_PTR(JSObject *, op));
}
class PropertyTree;
} /* namespace js */
struct JSScopeProperty {
friend struct JSScope;
friend class js::PropertyTree;
friend JSDHashOperator js::RemoveNodeIfDead(JSDHashTable *table, JSDHashEntryHdr *hdr,
uint32 number, void *arg);
friend void js::SweepScopeProperties(JSContext *cx);
jsid id; /* int-tagged jsval/untagged JSAtom* */
private:
union {
JSPropertyOp rawGetter; /* getter and setter hooks or objects */
JSObject *getterObj; /* user-defined callable "get" object or
null if sprop->hasGetterValue() */
JSScopeProperty *next; /* next node in freelist */
};
union {
JSPropertyOp rawSetter; /* getter is JSObject* and setter is 0
if sprop->isMethod() */
JSObject *setterObj; /* user-defined callable "set" object or
null if sprop->hasSetterValue() */
JSScopeProperty **prevp; /* pointer to previous node's next, or
pointer to head of freelist */
};
void insertFree(JSScopeProperty *&list) {
id = JSVAL_NULL;
next = list;
prevp = &list;
if (list)
list->prevp = &next;
list = this;
}
void removeFree() {
JS_ASSERT(JSVAL_IS_NULL(id));
*prevp = next;
if (next)
next->prevp = prevp;
}
public:
uint32 slot; /* abstract index in object slots */
private:
uint8 attrs; /* attributes, see jsapi.h JSPROP_* */
uint8 flags; /* flags, see below for defines */
public:
int16 shortid; /* tinyid, or local arg/var index */
JSScopeProperty *parent; /* parent node, reverse for..in order */
union {
JSScopeProperty *kids; /* null, single child, or a tagged ptr
to many-kids data structure */
JSScopeProperty **childp; /* dictionary list starting at lastProp
has a double-indirect back pointer,
either to sprop->parent if not last,
else to scope->lastProp */
};
uint32 shape; /* property cache shape identifier */
private:
/*
* Implementation-private bits stored in sprop->flags. See public: enum {}
* flags further below, which were allocated FCFS over time, so interleave
* with these bits.
*/
enum {
/* GC mark flag. */
MARK = 0x01,
/*
* Set during a shape-regenerating GC if the shape has already been
* regenerated. Unlike JSScope::SHAPE_REGEN, this does not toggle with
* each GC. js::SweepScopeProperties clears it.
*/
SHAPE_REGEN = 0x08,
/* Property stored in per-object dictionary, not shared property tree. */
IN_DICTIONARY = 0x20
};
JSScopeProperty(jsid id, JSPropertyOp getter, JSPropertyOp setter, uint32 slot,
uintN attrs, uintN flags, intN shortid)
: id(id), rawGetter(getter), rawSetter(setter), slot(slot), attrs(uint8(attrs)),
flags(uint8(flags)), shortid(int16(shortid))
{
JS_ASSERT_IF(getter && (attrs & JSPROP_GETTER), getterObj->isCallable());
JS_ASSERT_IF(setter && (attrs & JSPROP_SETTER), setterObj->isCallable());
}
bool marked() const { return (flags & MARK) != 0; }
void mark() { flags |= MARK; }
void clearMark() { flags &= ~MARK; }
bool hasRegenFlag() const { return (flags & SHAPE_REGEN) != 0; }
void setRegenFlag() { flags |= SHAPE_REGEN; }
void clearRegenFlag() { flags &= ~SHAPE_REGEN; }
bool inDictionary() const { return (flags & IN_DICTIONARY) != 0; }
public:
/* Public bits stored in sprop->flags. */
enum {
ALIAS = 0x02,
HAS_SHORTID = 0x04,
METHOD = 0x10,
PUBLIC_FLAGS = ALIAS | HAS_SHORTID | METHOD
};
uintN getFlags() const { return flags & PUBLIC_FLAGS; }
bool isAlias() const { return (flags & ALIAS) != 0; }
bool hasShortID() const { return (flags & HAS_SHORTID) != 0; }
bool isMethod() const { return (flags & METHOD) != 0; }
JSObject *methodObject() const { JS_ASSERT(isMethod()); return getterObj; }
jsval methodValue() const { return OBJECT_TO_JSVAL(methodObject()); }
JSPropertyOp getter() const { return rawGetter; }
bool hasDefaultGetter() const { return !rawGetter; }
JSPropertyOp getterOp() const { JS_ASSERT(!hasGetterValue()); return rawGetter; }
JSObject *getterObject() const { JS_ASSERT(hasGetterValue()); return getterObj; }
// Per ES5, decode null getterObj as the undefined value, which encodes as null.
jsval getterValue() const {
JS_ASSERT(hasGetterValue());
return getterObj ? OBJECT_TO_JSVAL(getterObj) : JSVAL_VOID;
}
JSPropertyOp setter() const { return rawSetter; }
bool hasDefaultSetter() const { return !rawSetter; }
JSPropertyOp setterOp() const { JS_ASSERT(!hasSetterValue()); return rawSetter; }
JSObject *setterObject() const { JS_ASSERT(hasSetterValue()); return setterObj; }
// Per ES5, decode null setterObj as the undefined value, which encodes as null.
jsval setterValue() const {
JS_ASSERT(hasSetterValue());
return setterObj ? OBJECT_TO_JSVAL(setterObj) : JSVAL_VOID;
}
inline JSDHashNumber hash() const;
inline bool matches(const JSScopeProperty *p) const;
inline bool matchesParamsAfterId(JSPropertyOp agetter, JSPropertyOp asetter, uint32 aslot,
uintN aattrs, uintN aflags, intN ashortid) const;
bool get(JSContext* cx, JSObject* obj, JSObject *pobj, jsval* vp);
bool set(JSContext* cx, JSObject* obj, jsval* vp);
inline bool isSharedPermanent() const;
void trace(JSTracer *trc);
bool hasSlot() const { return (attrs & JSPROP_SHARED) == 0; }
uint8 attributes() const { return attrs; }
bool configurable() const { return (attrs & JSPROP_PERMANENT) == 0; }
bool enumerable() const { return (attrs & JSPROP_ENUMERATE) != 0; }
bool writable() const {
// JS_ASSERT(isDataDescriptor());
return (attrs & JSPROP_READONLY) == 0;
}
bool hasGetterValue() const { return attrs & JSPROP_GETTER; }
bool hasSetterValue() const { return attrs & JSPROP_SETTER; }
bool hasDefaultGetterOrIsMethod() const {
return hasDefaultGetter() || isMethod();
}
bool isDataDescriptor() const {
return (attrs & (JSPROP_SETTER | JSPROP_GETTER)) == 0;
}
bool isAccessorDescriptor() const {
return (attrs & (JSPROP_SETTER | JSPROP_GETTER)) != 0;
}
#ifdef DEBUG
void dump(JSContext *cx, FILE *fp);
void dumpSubtree(JSContext *cx, int level, FILE *fp);
#endif
};
/* JSScopeProperty pointer tag bit indicating a collision. */
#define SPROP_COLLISION ((jsuword)1)
#define SPROP_REMOVED ((JSScopeProperty *) SPROP_COLLISION)
/* Macros to get and set sprop pointer values and collision flags. */
#define SPROP_IS_FREE(sprop) ((sprop) == NULL)
#define SPROP_IS_REMOVED(sprop) ((sprop) == SPROP_REMOVED)
#define SPROP_IS_LIVE(sprop) ((sprop) > SPROP_REMOVED)
#define SPROP_FLAG_COLLISION(spp,sprop) (*(spp) = (JSScopeProperty *) \
((jsuword)(sprop) | SPROP_COLLISION))
#define SPROP_HAD_COLLISION(sprop) ((jsuword)(sprop) & SPROP_COLLISION)
#define SPROP_FETCH(spp) SPROP_CLEAR_COLLISION(*(spp))
#define SPROP_CLEAR_COLLISION(sprop) \
((JSScopeProperty *) ((jsuword)(sprop) & ~SPROP_COLLISION))
#define SPROP_STORE_PRESERVING_COLLISION(spp, sprop) \
(*(spp) = (JSScopeProperty *) ((jsuword)(sprop) \
| SPROP_HAD_COLLISION(*(spp))))
inline JSScopeProperty *
JSScope::lookup(jsid id)
{
return SPROP_FETCH(search(id, false));
}
inline bool
JSScope::hasProperty(JSScopeProperty *sprop)
{
return lookup(sprop->id) == sprop;
}
inline JSScopeProperty *
JSScope::lastProperty() const
{
JS_ASSERT_IF(lastProp, !JSVAL_IS_NULL(lastProp->id));
return lastProp;
}
/*
* Note that sprop must not be null, as emptying a scope requires extra work
* done only by methods in jsscope.cpp.
*/
inline void
JSScope::setLastProperty(JSScopeProperty *sprop)
{
JS_ASSERT(!JSVAL_IS_NULL(sprop->id));
JS_ASSERT_IF(lastProp, !JSVAL_IS_NULL(lastProp->id));
lastProp = sprop;
}
inline void
JSScope::removeLastProperty()
{
JS_ASSERT(!inDictionaryMode());
JS_ASSERT_IF(lastProp->parent, !JSVAL_IS_NULL(lastProp->parent->id));
lastProp = lastProp->parent;
--entryCount;
}
inline void
JSScope::removeDictionaryProperty(JSScopeProperty *sprop)
{
JS_ASSERT(inDictionaryMode());
JS_ASSERT(sprop->inDictionary());
JS_ASSERT(sprop->childp);
JS_ASSERT(!JSVAL_IS_NULL(sprop->id));
JS_ASSERT(lastProp->inDictionary());
JS_ASSERT(lastProp->childp == &lastProp);
JS_ASSERT_IF(lastProp != sprop, !JSVAL_IS_NULL(lastProp->id));
JS_ASSERT_IF(lastProp->parent, !JSVAL_IS_NULL(lastProp->parent->id));
if (sprop->parent)
sprop->parent->childp = sprop->childp;
*sprop->childp = sprop->parent;
--entryCount;
sprop->childp = NULL;
}
inline void
JSScope::insertDictionaryProperty(JSScopeProperty *sprop, JSScopeProperty **childp)
{
/*
* Don't assert inDictionaryMode() here because we may be called from
* toDictionaryMode via newDictionaryProperty.
*/
JS_ASSERT(sprop->inDictionary());
JS_ASSERT(!sprop->childp);
JS_ASSERT(!JSVAL_IS_NULL(sprop->id));
JS_ASSERT_IF(*childp, (*childp)->inDictionary());
JS_ASSERT_IF(lastProp, lastProp->inDictionary());
JS_ASSERT_IF(lastProp, lastProp->childp == &lastProp);
JS_ASSERT_IF(lastProp, !JSVAL_IS_NULL(lastProp->id));
sprop->parent = *childp;
*childp = sprop;
if (sprop->parent)
sprop->parent->childp = &sprop->parent;
sprop->childp = childp;
++entryCount;
}
/*
* If SHORTID is set in sprop->flags, we use sprop->shortid rather
* than id when calling sprop's getter or setter.
*/
#define SPROP_USERID(sprop) \
((sprop)->hasShortID() ? INT_TO_JSVAL((sprop)->shortid) \
: ID_TO_VALUE((sprop)->id))
#define SLOT_IN_SCOPE(slot,scope) ((slot) < (scope)->freeslot)
#define SPROP_HAS_VALID_SLOT(sprop,scope) SLOT_IN_SCOPE((sprop)->slot, scope)
#ifndef JS_THREADSAFE
# define js_GenerateShape(cx, gcLocked) js_GenerateShape (cx)
#endif
extern uint32
js_GenerateShape(JSContext *cx, bool gcLocked);
#ifdef DEBUG
struct JSScopeStats {
jsrefcount searches;
jsrefcount hits;
jsrefcount misses;
jsrefcount hashes;
jsrefcount steps;
jsrefcount stepHits;
jsrefcount stepMisses;
jsrefcount tableAllocFails;
jsrefcount toDictFails;
jsrefcount wrapWatchFails;
jsrefcount adds;
jsrefcount addFails;
jsrefcount puts;
jsrefcount redundantPuts;
jsrefcount putFails;
jsrefcount changes;
jsrefcount changeFails;
jsrefcount compresses;
jsrefcount grows;
jsrefcount removes;
jsrefcount removeFrees;
jsrefcount uselessRemoves;
jsrefcount shrinks;
};
extern JS_FRIEND_DATA(JSScopeStats) js_scope_stats;
# define METER(x) JS_ATOMIC_INCREMENT(&js_scope_stats.x)
#else
# define METER(x) /* nothing */
#endif
inline JSScopeProperty **
JSScope::search(jsid id, bool adding)
{
JSScopeProperty *sprop, **spp;
METER(searches);
if (!table) {
/* Not enough properties to justify hashing: search from lastProp. */
for (spp = &lastProp; (sprop = *spp); spp = &sprop->parent) {
if (sprop->id == id) {
METER(hits);
return spp;
}
}
METER(misses);
return spp;
}
return searchTable(id, adding);
}
#undef METER
inline bool
JSScope::canProvideEmptyScope(JSObjectOps *ops, JSClass *clasp)
{
/*
* An empty scope cannot provide another empty scope, or wrongful two-level
* prototype shape sharing ensues -- see bug 497789.
*/
if (!object)
return false;
return this->ops == ops && (!emptyScope || emptyScope->clasp == clasp);
}
inline bool
JSScopeProperty::get(JSContext* cx, JSObject* obj, JSObject *pobj, jsval* vp)
{
JS_ASSERT(!JSVAL_IS_NULL(this->id));
JS_ASSERT(!hasDefaultGetter());
if (hasGetterValue()) {
JS_ASSERT(!isMethod());
jsval fval = getterValue();
return js_InternalGetOrSet(cx, obj, id, fval, JSACC_READ, 0, 0, vp);
}
if (isMethod()) {
*vp = methodValue();
JSScope *scope = pobj->scope();
JS_ASSERT(scope->object == pobj);
return scope->methodReadBarrier(cx, this, vp);
}
/*
* JSObjectOps is private, so we know there are only two implementations
* of the thisObject hook: with objects and XPConnect wrapped native
* objects. XPConnect objects don't expect the hook to be called here,
* but with objects do.
*/
if (obj->getClass() == &js_WithClass)
obj = obj->map->ops->thisObject(cx, obj);
return getterOp()(cx, obj, SPROP_USERID(this), vp);
}
inline bool
JSScopeProperty::set(JSContext* cx, JSObject* obj, jsval* vp)
{
JS_ASSERT_IF(hasDefaultSetter(), hasGetterValue());
if (attrs & JSPROP_SETTER) {
jsval fval = setterValue();
return js_InternalGetOrSet(cx, obj, id, fval, JSACC_WRITE, 1, vp, vp);
}
if (attrs & JSPROP_GETTER)
return !!js_ReportGetterOnlyAssignment(cx);
/* See the comment in JSScopeProperty::get as to why we can check for With. */
if (obj->getClass() == &js_WithClass)
obj = obj->map->ops->thisObject(cx, obj);
return setterOp()(cx, obj, SPROP_USERID(this), vp);
}
inline bool
JSScopeProperty::isSharedPermanent() const
{
return (~attrs & (JSPROP_SHARED | JSPROP_PERMANENT)) == 0;
}
extern JSScope *
js_GetMutableScope(JSContext *cx, JSObject *obj);
extern void
js_TraceId(JSTracer *trc, jsid id);
JS_END_EXTERN_C
#ifdef _MSC_VER
#pragma warning(pop)
#pragma warning(pop)
#endif
#endif /* jsscope_h___ */
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